As used herein, the term “crop” refers to desirable plants, including, in one aspect of the invention, turfgrasses. Turfgrasses are different from other grasses in three primary ways: turfgrasses can form a dense contiguous community, tolerate frequent mowing and tolerate traffic. Due to these unique qualities turfgrasses are used extensively in our urban culture including golf courses, athletic fields, parks, cemeteries, roadsides and home lawns. Proper turfgrass management is critical to its long-term sustainability and the safety of the playing surfaces where it's utilized. Turfgrass is managed according to five primary cultural practices; 1) mowing, 2) fertilization, 3) cultivation, 4) irrigation and 5) pest control.
While turfgrasses are often grown as part of an athletic field, golf courses and/or lawns, other types of grasses may also comprise a desirable crop plant. For example, grasses may be grown for grazing by cattle. Such grasses may comprise forage grasses, turfgrasses, or a combination thereof. Another example of a crop that may also be grown for harvest is hay.
Pest control employs preventative and/or curative approaches to protecting desirable crop species, such as grasses, from potentially damaging weeds, insects, and/or diseases. Traditionally, turfgrass managers have implemented an Integrated Pest Management (IPM) program to maintain pest populations below threshold levels. The IPM approach allows the judicious use of pesticides to maintain pest populations at an acceptable level to maintain a healthy turfgrass stand. A pesticide is a broad term used to describe any substance that prevents, destroys, repels or mitigates any pest. Pesticides are further categorized according to their intended targets (i.e. herbicides, fungicides, insecticides, etc.). Herbicides, pesticides targeting weeds only, accounted for the highest usage of pesticides in the home and garden sector with 66 million pounds applied in 2007 (U.S. Environmental Protection Agency, Pesticides Industry Sales and Usage 2006 and 2007 Market Estimates).
The concern regarding pesticide applications has increased tremendously, particularly where there is potential risk of exposure to children such as lawn areas, athletic fields and parks/playgrounds. The primary concern regarding low, nonacute, repetitive and combined exposures are increased risk of cancer, abnormal neurodevelopment, asthma, perturbation of gestational growth, and endocrine-mimicking effects (US AAP 2012 and Can Fam Phys, 2007). J. R. Roberts, C. J. Karr, Pesticide Exposure in Children, Pediatrics Vol. 130, No. 6 (2012); K. L. Bassil, et al, Cancer Health Effects of Pesticides, Canadian Family Physician, Vol. 53 (2007). These very serious concerns have resulted in pesticide restrictions related to athletic fields in 41 out of 50 states, according to the Sports Turf Managers Association. Connecticut has banned all pesticide applications on school grounds and athletic fields serving grades pre-k through grade 8. There is discussion to expand the scope of this law to high school and public grounds. The state of New York passed the Childs Safe Playing Field Act that essentially bans pesticide use on schools grounds, day care centers and athletic fields through grade 12. Additionally, several municipalities across the U.S. have banned pesticides on parks, open space parcels and public rights of way. This includes 7 states, 18 cities, and 92 parks/playgrounds. Concerns regarding pesticide impacts on human health and the environment have even advanced to the university and college level where some campuses or specific areas of campus have been declared pesticide-free as they embrace more sustainable approaches.
Turfgrass breeding efforts have resulted in improved cultivars of different turfgrass species that have better insect and disease resistance helping to reduce the susceptibility of some turfgrass species. Additionally, entomopathogenic nematodes have been shown to biologically control some of the most damaging root feeding insects. See, Georgis, R., and R. Gaugler, Predictability in biological control using entomopathogenic nematodes. J. Econ. Entomol. 84(3): p. 713-720. However, a consistent method of weed control is not available. This leaves many high quality turfgrass areas susceptible to weed infestations on a perennial basis. This is particularly a concern in high traffic areas such as athletic fields where turfgrass cover is continually reduced and opportunistic weeds are able to germinate, develop quickly, and potentially dominate a turfgrass stand in a very short period of time.
Previous research has investigated the effects of utilizing existing equipment such as spring-tine harrows or vertical cutting units to damage weeds and create a competitive advantage for turfgrasses on football pitches (Larsen, S. V., P. Kristoffersen, and J. Fischer, Turfgrass management and weed control without pesticides on football pitches in Denmark. Pest Manage. Sci. 60(6): p. 579-587). However, these methods were thought to be too injurious to the established turfgrass resulting in modest weed control and sometimes increased weed pressure.
Research has shown that perennial broadleaf weeds and annual grassy weeds are less traffic tolerant than desirable turfgrass species. Miller, N. A., and J. J. Henderson 2012, Organic management practices on athletic fields: Part 1: The effects on color, quality, cover, and weed populations. Crop Sci. 52(2): p. 890-903 and J. T Brosnan et al, Large Crabgrass, White Clover, and Hybrid Bermudagrass Athletic Field Playing Quality in Response to Simulated Traffic, Crop. Sci. 54:1838-1843 (2014). Therefore, when intense traffic is applied over time to a turfgrass stand containing perennial broadleaf weeds and annual grassy weeds, the desirable turfgrasses persist and the weeds do not. Traffic is a combination of wear (i.e. tearing and bruising of leaf tissue) and soil compaction (i.e. forcing soil solids closer together). Research has also indicated that when traffic components (wear and compaction) are implemented separately to different areas and their detrimental effects are compared, wear is more detrimental to the quality of vegetative cover than compaction. See, Dest, W. M., J. S. Ebdon, and K. Guillard, Differentiating between the influence of wear and soil compaction and their interaction of turfgrass stress, Int. Turfgrass Soc. Res. J. 11 (Part 2) p. 1067-1083.
Weeds substantially reduce the aesthetic quality of turfgrass stands, but most importantly are less traffic tolerant than turfgrasses. Therefore, once weeds dominate an existing turfgrass stand, weeds are unable to persist under the constant traffic and vegetative cover is drastically reduced. Athletic fields with reduced vegetative cover have been linked to higher surface hardness values and increased risk of surface related injuries. See, Dest, W. M., and J. S. Ebdon. Study: Natural turf use levels. SportsTurf. 27(5) p. 8, 10-11 and Brosnan et al. 2014. However, chemical applications, such as selective herbicides, are more likely to be limited on athletic fields due to human exposure concerns.
Accordingly, there is a need for an apparatus, system and method of growing and improving desirable, wear-tolerant plants and reducing undesirable weeds that may compete with this growth. There is further a need for an apparatus, system and method of reducing weeds in turfgrass and other crops without the application of selective herbicides. There is also a need for an apparatus, system and method of producing improved wear tolerance in turfgrass.